package implementqueuebystack

// 使用栈实现队列
type MyQueue struct {
    inStack, outStack []int
}

func Constructor() MyQueue {
    return MyQueue{}
}

func (q *MyQueue) Push(x int) {
    q.inStack = append(q.inStack, x)
}

func (q *MyQueue) in2out() {
    for len(q.inStack) > 0 {
        q.outStack = append(q.outStack, q.inStack[len(q.inStack)-1])
        q.inStack = q.inStack[:len(q.inStack)-1]
    }
}

func (q *MyQueue) Pop() int {
    if len(q.outStack) == 0 {
        q.in2out()
    }
    x := q.outStack[len(q.outStack)-1]
    q.outStack = q.outStack[:len(q.outStack)-1]
    return x
}

func (q *MyQueue) Peek() int {
    if len(q.outStack) == 0 {
        q.in2out()
    }
    return q.outStack[len(q.outStack)-1]
}

func (q *MyQueue) Empty() bool {
    return len(q.inStack) == 0 && len(q.outStack) == 0
}
